The invention relates to a product, its applications, and a manufacturing method, the product comprising a film or sheet with the form of a tape, hereinafter referred to as “the film”, made of an edible or non-edible material, meant for wrapping food products, that has been curved over itself and around a support tube which has a longitudinal axis, to form a cylinder in which the longitudinal side edges of the film, which are parallel to the longitudinal axis of the support tube, are overlapping.
This cylinder is shirred or wrinkled in an accordion-like shape forming folds, or wrinkles perpendicular to the axis of the cylinder, i.e., transverse folds, in order to contain in it the maximum amount possible of said film. Additionally, as can be seen in FIG. 1, the transverse folds can be uniformly distributed. The cylinder formed by the film curved onto itself and shirred can have an internal support consisting of a tube of a stiff material. The diameter of this tube is smaller than that of the cylinder formed by the film, so that the latter can be suitably shirred or wrinkled on the tube without losing the overlapping of its longitudinal side edges.
The above assembly can be externally coated with an elastic, semi-elastic or non-elastic tubular net in an amount identical in length to the film, placed coaxially to the film and the tube and compressed or shirred in the same extent as the film, so that it occupies the same length. The beginning of the compressed or shirred tubular net can be slightly displaced with respect to the beginning of the shirred film, so that a few centimeters of the latter are left uncovered. Between the shirred film and the compressed tubular net can be placed a cylindrical separation sheet of any material, such as a plastic film. This separation sheet is attached to the support tube at the end opposite the aforementioned beginning of the film curved onto itself and shirred, not covered by the compressed or shirred tubular net.
The above assembly forms a system that by way of a simultaneous unshirring of the film and the net can, continuously or discontinuously, provide a double wrapping formed by the overlapping film and the tubular net that can be filled by closing the film and the net jointly on the open end and stuffing inside a solid or semisolid product with a stuffing horn placed inside the support tube of the assembly. The area of shirred film not coated by the compressed or shirred tubular net ensures that the latter will not prevent the shirred film from unshirring easily because of the compression force exerted on it. As the film and the net are unshirred to form the wrapping, the front ends of the shirred film and net move back in the same extent, so that there is always an area of uncoated and free shirred film. The separation sheet allows the film to become unshirred uniformly and ensures that the portion of shirred film not coated by the compressed net is not carried away by the latter as it unfolds.
The product described can be used for manual or automatic packaging of food products that may or may not be later subjected to any processes of drying, maturing, curing, cooking, sterilization, etc., in which the film casing and outer net assembly are required.
The present invention mainly lies in the field of packaging of food products, and more specifically in the industry of meat products. A great variety of products are wrapped in film for processing, handling and/or conservation. The use of the film is often combined with that of the tubular net, finding specific application in special products where the appearance of the product is an important aspect.
Tying certain meat pieces or cuts with a string before cooking it is a traditional practice used both in homes and industry, and has been known since ancient times. This operation allows on one hand to condition certain meat cuts in manner suitable for cooking or industrial heat treatment when their shape or configuration requires so. This practice also allows stuffing said pieces with other foods and, by keeping the meat pieces joined to each other during cooking, allows a proper bonding of the product.
The string method described soon gave way to other systems facilitating the onerous task of tying the meat pieces. The most commonly used system nowadays is the use of a tubular net, elastic or otherwise, which can be applied more quickly than the string with simple devices.
When, as in the case of the meat industry, meats are used that have been injected brine and that are later subjected to massaging processes, the great bonding capacity of these meats makes the nets stick after the heat treatment and even become coated by the meat itself after the bonding, so that their removal is very difficult. In any event, after the net is eliminated, the meat is considerably damaged superficially and has a poor appearance.
To solve this problem, collagen films began to be interposed between the meat and the net to prevent the net from adhering to the meat and allowing its simple removal, resulting in products with a proper appearance. The use of artificial collagen films also provided other advantages, such as a shiny surface, permeability to smoke, retaining liquids during cooking resulting in more juicy products and higher yields; in addition, the film is completely edible. The procedure for manufacturing said collagen films, as well as the subsequent improvements and changes, are described in U.S. Pat. No. 642,922 and U.S. Pat. No. 5,885,634 (Areso, 1999).
The film and net assembly thus defines a wrapping in which the main function of the film is to contain liquid parts, prevent excessive evaporation during the heat treatment, allow smoking, improve the shine, color and appearance of the surface of the product and facilitate the elimination of the net and of the film itself if it is not edible; it must also be sufficiently soft to allow the net to make its mark on the product giving it its characteristic appearance.
Tubular nets and films are currently applied in the food product industry either manually or mechanically. For this, the films are supplied in cut sheets or in rolls of varying length, which can range from 5 to 250 meters. Nets are supplied as rolls of at least 50 meters length. A manual application method involves wrapping the food product with film and covering it with the net by making it pass through a hollow metal cylinder or tube that serves as a support for a given amount of tubular net that has been shirred or compressed on it coaxially, obtaining the product out of the other end of the cylinder fully covered by the net, which is thus coating it. This product is described in U.S. Pat. No. 4,621,482 (Crevasse, Gammon, Sullivan, 1986). An even simpler procedure is described in U.S. Pat. No. 4,719,116 (Crevasse, 1988).
The mechanical procedure is performed by “applicators” that wrap the product with the film and net simultaneously. A typical applicator consists of a roller bearing a film coil, a device that conforms the film into a tube and a tube that runs inside the conformed film tube and through which the food product is made to pass. Concentric to the previous assembly, a tube is disposed in which a certain amount of net has been compressed. The end of the tube formed by the film and the end of the compressed net are taken jointly forward of the open end of the stuffing horn and closed jointly by a clip, knot or any other suitable method, with the system ready to be stuffed whether by mechanically pumping a product or by a piston driven manually or pneumatically. When the product is impelled out of the tube, it simultaneously pulls on the film and the tubular net, thereby becoming wrapped in both.
This procedure and the device for effecting it are described in U.S. Pat. No. 4,910,034 (Winkler, 1990) and U.S. Pat. No. 4,958,477 (Winkler, 1990), respectively. Also described are devices for compressing the nets, in U.S. Pat. No. 5,273,481 (Sullivan, 1993) and U.S. Pat. No. 4,924,552 (Sullivan, 1990). The following operation is closing the wrapper by a double clip, knot, etc. and cutting the piece of meat to leave the machine ready to repeat the operation. There are machines that incorporate a double clipper and that execute the operations automatically.
In any case, the sequence of operations carried out is as follows:
1) Transporting and installing the applicator in the packaging line. Except for applicators integrated in packaging lines specific for this type of operations, this operation must be performed at the start of each working session. It is part of the equipment setup process and during the time required to perform this the line remains unproductive.
2) Loading the roll of film in the applicator. This must be done each time the roll is finished. The length of film loaded in each roll will determine the frequency of stoppages. This operation is time intensive and must be performed carefully to obtain a properly overlapping film. It is especially complicated in cases where the overlap is on the bottom. This is done such that the film loses the overlap at the outlet of the stuffing horn each time a piece is finished, given its tendency to fall under gravity.
3) Loading the net tube. This must be performed each time a load of a tubular net is finished, which occurs quite often as the amount that may be loaded each time is quite small and ranges from 8 to 18 meters approximately, depending on the diameter and length of the tube and the net characteristics. This operation can be performed manually, but it is more common to use devices known as loaders that simplify the operation considerably. These loaders are described, as mentioned above, in U.S. Pat. No. 5,273,481 (Sullivan, 1993) and U.S. Pat. No. 4,924,552 (Sullivan, 1990).
4) Joint clipping or tying of the first end of film and net. This operation is related to changing the net tube or roll of film, and precedes the start of each stuffing series.
5) Applicator cleaning. This must be performed at least at the end of each working session, each time the device is accidentally dirtied, or as required by hygiene regulations.
It must be pointed out that each type of applicator is only valid for a narrow range of gauges of the final product, so that it is necessary to add to the above operations that of changing the applicator and all components whenever the product is changed to conform to demand, which requires flexibility in production, which is increasingly common in current production processes.
In addition to these minimal operations, it is often necessary to stop the process due to a number of problems inherent to it that the state of the art has not yet managed to solve satisfactorily. These problems include breakage of the film due to excessive rubbing against the applicator parts in contact with it, or due to an excessively tight winding. This problem occurs when the force required to pull it is greater than the strength of the film and is common when the film is moist, dry or dirty, as well as when the parts in contact with the film are moist or dirty.
Certain films stick when moist to the contact surfaces of the applicators due to their surface tension. In other cases they lose strength when in contact with water or when excessively dry. Sometimes a low humidity can increase friction. In short, the humidity conditions of the film significantly affect their behavior during application. Together with the fact that most films are sensitive to changes in humidity and that it is difficult to maintain stable conditions in industrial packaging rooms because of the humidity and low temperature, this means that application of packaging films is a complicated, cumbersome and accident-prone task.
When the above-described problems reach a certain intensity, they lead to the film breaking and the corresponding stoppages that cost time, packaging material, and raw material which must be discarded. In cases where variations in the traction force on the film or the net are not great enough to cause tears, other problems derived from these variations arise. For example, when the traction force required is greater than normal, the products are stuffed under a high pressure and will adopt an undesirable spherical shape, thus increasing their maximum diameter and often losing the film overlap because of this. If the traction force is lower, loose pieces are produced with a cylindrical shape having excessive length that must be recovered manually. It often occurs that a piece that at the beginning is stuffed with a high resistance to traction will, when the stuffing force exceeds said friction, suddenly release an excessive amount of packaging material also resulting in exaggeratedly loose and cylindrical pieces.
Similar problems are caused due to loading the nets on the pneumatic loaders, where oftentimes portions of net loaded are squashed under the net portions loaded previously. As the new material loaded at the end is the first to be used in the application, the squashed fragments will be released with greater difficulty resulting in spherical and tight pieces, or loose cylindrical pieces when the previously described phenomenon occurs.
Another common problem is loss of the overlapping. The mechanical problems inherent to the process mean that the edge overlapping will often be lost. When this occurs, the product is not properly coated by the film resulting in numerous problems, mainly aesthetic and of adherence of the net, which cannot be later removed without tears resulting in lower quality products.
Another problem of this system results from the low pressure under which the products are stuffed in the film and net that hinders a correct de-aeration of the products. In these conditions it is necessary to perforate the film to allow the trapped air to be released during the cooking process to prevent the appearance of surface air bubbles giving a poor appearance to the product. Certain films, particularly the stronger ones, can be perforated before they are used, but in other cases it is necessary to do so after the packaging, implying an additional operation.
All of the above operations, together with their difficulty and the ease with which breakages occur in current systems and other interruptions, make the packaging of products in films and nets a slow, complicated and cumbersome task.